The Spanish side, who sit ninth in La Liga, beat Molde in Europa League last-16 to book a quarter-final with United.
The first leg will be played in Andalusia on Thursday.
Asked if he was surprised Granada have reached the final eight, Solskjaer said: "No, not surprised at all. It's unbelievable how much attitude, desire, team spirit, values, how much that can do for a team, for players.
"They're very good at - and better than most - at the things that don't cost anything which is just what I'm talking about. I mean that as a compliment. I think the value of team spirit, camaraderie, organisation is so important for a team.
"But then they also have the individual quality and experience in a few players that will have been very important for them.
"But in football you're never surprised when teams that get promoted and do well, because they get promoted for a reason. It's quality and the team spirit and morale in the squad, and the manager's values."